ch06/invest1/InvestmentRunner.java
 /**
 This program computes how long it takes for an investment
 to double.
 */
 public class InvestmentRunner
 {
 public static void main(String[] args)
 {
 final double INITIAL_BALANCE = 10000;
 final double RATE = 5;
 Investment invest = new Investment(INITIAL_BALANCE, RATE);
 Invest.waitForBalance(2 * INITIAL_BALANCE);
 int years = invest.getYears();
 System.out.printf("The investment doubled after"
 + years + " years"
}
 }